// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_FIELD_INDEX_INL_H_
#define V8_FIELD_INDEX_INL_H_

#include "src/field-index.h"
#include "src/objects-inl.h"
#include "src/objects/descriptor-array-inl.h"

namespace v8 {
namespace internal {

    FieldIndex FieldIndex::ForInObjectOffset(int offset, Encoding encoding)
    {
        DCHECK_IMPLIES(encoding == kWord32, IsAligned(offset, kInt32Size));
        DCHECK_IMPLIES(encoding == kTagged, IsAligned(offset, kTaggedSize));
        DCHECK_IMPLIES(encoding == kDouble, IsAligned(offset, kDoubleSize));
        return FieldIndex(true, offset, encoding, 0, 0);
    }

    FieldIndex FieldIndex::ForPropertyIndex(const Map map, int property_index,
        Representation representation)
    {
        DCHECK(map->instance_type() >= FIRST_NONSTRING_TYPE);
        int inobject_properties = map->GetInObjectProperties();
        bool is_inobject = property_index < inobject_properties;
        int first_inobject_offset;
        int offset;
        if (is_inobject) {
            first_inobject_offset = map->GetInObjectPropertyOffset(0);
            offset = map->GetInObjectPropertyOffset(property_index);
        } else {
            first_inobject_offset = FixedArray::kHeaderSize;
            property_index -= inobject_properties;
            offset = PropertyArray::OffsetOfElementAt(property_index);
        }
        Encoding encoding = FieldEncoding(representation);
        return FieldIndex(is_inobject, offset, encoding, inobject_properties,
            first_inobject_offset);
    }

    // Returns the index format accepted by the HLoadFieldByIndex instruction.
    // (In-object: zero-based from (object start + JSObject::kHeaderSize),
    // out-of-object: zero-based from FixedArray::kHeaderSize.)
    int FieldIndex::GetLoadByFieldIndex() const
    {
        // For efficiency, the LoadByFieldIndex instruction takes an index that is
        // optimized for quick access. If the property is inline, the index is
        // positive. If it's out-of-line, the encoded index is -raw_index - 1 to
        // disambiguate the zero out-of-line index from the zero inobject case.
        // The index itself is shifted up by one bit, the lower-most bit
        // signifying if the field is a mutable double box (1) or not (0).
        int result = index();
        if (is_inobject()) {
            result -= JSObject::kHeaderSize / kTaggedSize;
        } else {
            result -= FixedArray::kHeaderSize / kTaggedSize;
            result = -result - 1;
        }
        result = static_cast<uint32_t>(result) << 1;
        return is_double() ? (result | 1) : result;
    }

    FieldIndex FieldIndex::ForDescriptor(const Map map, int descriptor_index)
    {
        PropertyDetails details = map->instance_descriptors()->GetDetails(descriptor_index);
        int field_index = details.field_index();
        return ForPropertyIndex(map, field_index, details.representation());
    }

} // namespace internal
} // namespace v8

#endif // V8_FIELD_INDEX_INL_H_
